a) What is (A + N) mod 26 in this system?
b) What is (B + 6) mod 26 in this system?
c) What is (Y - 4) mod 26 in this system?
d) What is (C - 9) mod 26 in this system?

Problem 2

a) The remainder of any positive integer when divided by 100 is the integer made of the two rightmost digits.

b) The remainder of any positive integer when divided by 1000 is the integer made of the three rightmost digits.
c) If a ≡ x1 (mod m) and b ≡ y1 (mod m), then we will have ab ≡ x1y1 (mod m). True or False?

1.)
a.) A + N = 1 + 14 ≡ 15 mod 26 in this system.
b.) To what value is B equal to?
c.) To what value is Y equal to?
d.) To what value is C equal to? You may want to add 26.

2.)
a.) Any integer is of the form 100 * k + r where k is any integer and r are the two rightmost digits.
b.) Can you do something similar as for a.)?
c.) Let a = k * m + x1 and Let b = l * m + y1. Can you compute a * b mod m?